This invention is directed at an asphaltic composition and a method for producing the asphaltic composition. More specifically, the present invention is directed at an asphaltic composition suitable for use in combination with aggregate as a paving composition having a reduced gas oil content.
One source for asphalt is the residuum from the fractionation of crude oil. During typical crude oil processing, the crude is passed through a series of distillation towers which remove the more volatile components from the hydrocarbon feed. In prior art processes, the amount of volatile components, such as gas oil, which could be removed from the feed was limited by the final viscosity of the residuum. While the unit value of gas oil generally exceeds the unit value of residuum for asphaltic applications, removal of an excessive amount of gas oil from the residuum may increase the viscosity of the residuum above the allowable maximum for asphaltic compositions, such as paving asphalt. In paving applications, excessively viscous asphalt is not desired, since the asphalt would not meet product specifications and would not exhibit the desired properties, such as flexibility, at the temperature extremes. Typically, in paving applications, the viscosity of the vacuum residuum or bitumen utilized in paving applications ranges between about 400 and about 4800 poise at 60.degree. C.
The admixture of fatty acids with bitumen in asphaltic paving compositions is known for improving the adhesion of the asphalt to aggregate.
U.S. Pat. No. 2,517,564 discloses the addition of polymerized sulfides and fatty acids to asphalt. This patent discloses that the concentration of each additive should range between 0.2% and 3% by weight.
U.S. Pat. No. 2,673,814 discloses the addition of from about 0.1 to about 30 wt.%, preferably about 3 to about 10 wt.% of the propane insoluble fraction obtained in the propane extraction of crude fatty materials, such as animal, marine and vegetable fats, fatty oils or fatty acids split therefrom the bitumen to improve asphalt adherence to aggregate.
U.S. Pat. Nos. 4,422,878 and 3,539,370 disclose that the addition of fatty acids improves the physical properties when fiber or metal compounds are added to the asphalt to improve the paving composition.
U.S. Pat. No. 4,436,896 discloses the manufacture of a synthetic asphalt by admixing 5-60 wt. % gilsonite with 95-40 wt. % tall oil or tall oil pitch.
U.S. Pat. No. 3,956,001 discloses the use of stearic acid in combination with another additive to retard surface hardening or skin formation when admixed with asphalts having a viscosity of about 2000 poise at 140.degree. F.
U.S. Pat. Nos. 2,632,712, 4,373,960, 4,453,980 and U.K. Pat. No. 1,379,392 all disclose cut back asphaltic compositions including fatty acids which are useful as liquids for surface dressing of roads.
However, none of the above-noted patents discloses the admixture of fatty acids with an asphaltic residuum having a viscosity of at least 6000 poise at 60.degree. C. to reduce the viscosity.
Accordingly, it would be desirable to remove additional volatile compounds, such as gas oil, from a residuum, yet still be able to utilize the residuum in asphaltic paving compositions meeting current asphaltic product specifications.
It would also be desirable to provide a method for reducing the viscosity of asphaltic compositions into the range of current asphaltic cement product specifications without the addition of gas oil.
It would also be desirable to remove gas oil from asphaltic compositions and counterbalance the resulting viscosity increase by the addition of reduced quantitites of commercially less valuable compositions.
It also would be desirable to provide an asphaltic composition having improved aggregate adhesion which avoids the use of costly additives required with conventional asphaltic compositions.
The present invention is directed at an asphaltic composition and method of preparing same comprising:
A. about 80 to about 99 wt. % of a hydrocarbon residuum having a viscosity of at least 6000 poise at 60.degree. C.; and,
B. about 1 to about 20 wt. % fatty acid.